Black borders around video output?
Figured it out don't worry!

I don't know how or why it worked, but I basically just tested a sample animation a couple of times using the same format above but in different blender files until eventually, (and miraculously) the borders disappeared on their own. It seems my Blender was a bit buggy.  

However, I wouldn't recommend this if it doesn't work for an extended period of time, but mine luckily worked after 2 or 3 tries.